Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$230.52	4.859%	$241.721	$241.72	$241.70	$241.70
Purchase #2	$125.42	4.863%	$131.5192	$131.52	$131.50	$131.50
Purchase #3	$36.51	7.525%	$39.2574	$39.26	$39.25	$39.30
Purchase #4	$103.64	9.182%	$113.1562	$113.16	$113.15	$113.20
Purchase #5	$19.63	3.492%	$20.3155	$20.32	$20.30	$20.30
Purchase #6	$40.40	9.680%	$44.3107	$44.31	$44.30	$44.30
Purchase #7	$80.92	9.391%	$88.5192	$88.52	$88.50	$88.50
7 purchase totals =	$637.04		$678.7992	$678.81	$678.70	$678.80